Regional Differences in the Response of Rainfall to Convectively Coupled Kelvin Waves over Tropical Africa
Regional Differences in the Response of Rainfall to Convectively Coupled Kelvin Waves over Tropical Africa
复制标题
热带非洲降雨对对流耦合开尔文波响应的区域差异
作者：
L. Jackson;R. Keane;D. Finney;J. Marsham;D. Parker;C. Senior;R. Stratton
对流的表示仍然是全球模型中最重要的偏差来源之一，需要评估方法来表明模型提供了正确的平均状态和可变性，这两者都是出于正确的原因。在这里，我们发展了一种新的方法来评估该地区由对流耦合开尔文波(CCKW)引起的降水变异性。在OLR中定义了CCKW循环的位相周期，并将其用于合成降水异常。我们描述了4月份热带非洲上空观测到的(TRMM)降水对CCKW的响应，并评估了区域气候模式(RCM)模拟的性能：参数化对流模拟(P25)和第一次泛非对流允许模拟(CP4)。极端降水和干旱日数的出现与CCKW活动有关。聚焦于区域差异，我们首次表明，西非和几内亚湾之间存在一个偶极子，涉及到陆地/离岸降水的变化，而向赤道非洲西部向增强降水的过渡发生在赤道非洲东部过渡之前的一个阶段。用于驱动RCM的全球模式模拟了CCKW，平均幅度为75%-82%的观测值。RCMS模拟了对CCKW的相干响应，并捕捉到了降水中的大尺度空间格局和位相关系，尽管模拟的降雨响应弱于观测值，并且存在距离赤道较大的区域偏差。与CP4相比，P25对TRMM平均降水异常的模拟更接近TRMM，尽管CP4更接近于模拟干旱天的响应。
The representation of convection remains one of the most important sources of bias in global models, and evaluation methods are needed that show that models provide the correct mean state and variability, both for the correct reasons. Here we develop a novel approach for evaluating rainfall variability due to convectively coupled Kelvin waves (CCKWs) in this region. A phase cycle was defined for the CCKW cycle in OLR and used to composite rainfall anomalies. We characterize the observed (TRMM) rainfall response to CCKWs over tropical Africa in April and evaluate the performance of regional climate model (RCM) simulations: a parameterized convection simulation (P25) and the first pan-Africa convection-permitting simulation (CP4). TRMM mean rainfall is enhanced and suppressed by CCKW activity, and the occurrence of extreme rainfall and dry days is coupled with CCKW activity. Focusing on regional differences, we show for the first time that there is a dipole between West Africa and the Gulf of Guinea involving onshore/offshore shifts in rainfall, and the transition to enhanced rainfall over west equatorial Africa occurs one phase before the transition over east equatorial Africa. The global model used to drive the RCMs simulated CCKWs with mean amplitudes of 75%–82% of observations. The RCMs simulated coherent responses to the CCKWs and captured the large-scale spatial patterns and phase relationships in rainfall although the simulated rainfall response is weaker than observations and there are regional biases that are bigger away from the equator. P25 produced a closer match to TRMM mean rainfall anomalies than CP4 although the response in dry days was more closely simulated by CP4.
影响因子：
4.9
作者：
C. Birch;S. Webster;Simon C. Peatman;D. Parker;A. Matthews;Y. Li;M. E. Hassim
通讯作者：
C. Birch;S. Webster;Simon C. Peatman;D. Parker;A. Matthews;Y. Li;M. E. Hassim
DOI：
10.5194/gmd-2016-194-supplement
发表时间：
2017
期刊：
--
影响因子：
--
作者：
D. Walters;I. Boutle;M. Brooks;T. Melvin;R. Stratton;S. Vosper;H. Wells;K. Williams;N. Wood
通讯作者：
D. Walters;I. Boutle;M. Brooks;T. Melvin;R. Stratton;S. Vosper;H. Wells;K. Williams;N. Wood
影响因子：
3.1
作者：
Yang G
通讯作者：
Yang G